Update documentation for erf support in Parser (#3874)

Docs/sphinx_documentation/source/Basics.rst

@@ -395,8 +395,8 @@ AMReX provides a parser in ``AMReX_Parser.H`` that can be used at runtime to eva
 expressions given in the form of string.  It supports ``+``, ``-``, ``*``,
 ``/``, ``**`` (power), ``^`` (power), ``sqrt``, ``exp``, ``log``, ``log10``,
 ``sin``, ``cos``, ``tan``, ``asin``, ``acos``, ``atan``, ``atan2``, ``sinh``, ``cosh``,
-``tanh``, ``asinh``, ``acosh``, ``atanh``, ``abs``, ``floor``, ``ceil`` and ``fmod``.
-The minimum and maximum of two
+``tanh``, ``asinh``, ``acosh``, ``atanh``, ``abs``, ``floor``, ``ceil``, ``fmod``,
+and ``erf``. The minimum and maximum of two
 numbers can be computed with ``min`` and ``max``, respectively.  It supports
 the Heaviside step function, ``heaviside(x1,x2)`` that gives ``0``, ``x2``,
 ``1``, for ``x1 < 0``, ``x1 = 0`` and ``x1 > 0``, respectively.